Some electronic apparatuses or information processing apparatuses, such as server apparatuses, hold many plug-in units (substrates) in their casings. An electronic component mounted on a plug-in unit generates heat in operation, and the plug-in unit is often air-cooled by an air cooling mechanism including a cooling fan.
Typically, an air cooling mechanism includes a plurality of cooling fan units, and they are arranged below the portion in which a plurality of plug-in units is held. The plug-in units can be cooled by the plurality of cooling fan units actuated so as to supply air flow toward the plug-in units from below the plug-in units. For such an air cooling mechanism, the plurality of cooling fan units are arranged in line in the lower portion of the apparatus. The cooling fan units can be individually detached from the casing of the apparatus.
For example, if one of the plurality of cooling fan units breaks down, only that broken cooling fan unit may be detached from the casing of the apparatus in order to be repaired. In this case, the location from which the cooling fan unit has been detached becomes an opened area, and air flow may leak through the opened area to outside the casing. For example, even if air flow from a cooling fan unit adjacent to the broken cooling fan unit travels obliquely in the direction of the plug-in unit corresponding to the broken cooling fan unit, because an opened area lies in the location from which the cooling fan unit has been detached, the air flow may be partially reflected by the plug-in unit and may exit through the opened area to outside the casing. In this case, the air flow from the cooling fan units does not efficiently travel in the vicinity of the plug-in unit. Accordingly, this may lead to decreased efficiency of cooling the plug-in unit that was cooled by the broken cooling fan unit and may result in overheating of that plug-in unit.
For example, Japanese Laid-open Patent Publication No. 2006-261276 discloses the following technique: an air cooling mechanism that reduces a decrease in cooling efficiency occurring when one of cooling fans included in an electronic device is inactive. The air cooling mechanism includes shielding plates disposed on the outer regions of the cooling fans. A leakage of air flow from an inactive cooling fan can be prevented by closing of the shielding plate corresponding to that inactive cooling fan.